Reducing gasoline vapor loss in fuel tank systems is becoming increasingly important in the automobile industry. A solution to this problem has been to reduce the diameter of an outlet end of a fuel tank filler neck relative an inlet end. While this approach has achieved some success, the success has been limited because as the diameter of the filler neck is decreased, the resistance to gasoline flow is increased. This increased resistance has caused other problems, notably pressure build up in the filler neck, often causing the fuel nozzle to shut off before the fuel tank is full.
Permeability of materials from which the filler tube assembly is manufactured also presents another design issue because the fuel vapors may diffuse through the fuel tank system components; various types of mild steels, for example, permit fuel vapor diffusion. Such fuel vapor diffusion further increases as steel components corrode over time.
A manufacturing issue with current filler neck designs is the method by which the diameter of inlet and of the filler neck is increased relative the diameter of the outlet end in order to provide a sufficient diameter to accept a gas nozzle during refueling. While filler necks are often made by a process of repeated reductions and expansions of a seamed, welded tube, this mechanical process structurally weakens the tube, resulting in an increasing tendency for the tube to leak at the seam.
To address this issue, manufacturers have begun using a seamless tube, which addresses the seam-leak problem but requires mechanically joining the outlet end of the filler neck to a separate filler tube and coupling a nozzle retainer. Such prior art attempts will include U.S. patent application Ser. No. 09/454,103, now U.S. Pat. No. 6,330,893; U.S. patent application Ser. No. 09/998,113, now U.S. Pat. No. 6,588,459; and U.S. patent application Ser. No. 10/615,485, filed Jul. 8, 2003; each of which is incorporated herein by reference. While these designs are improvements, such a three-piece fuel filler tube assembly is relatively expensive to manufacture and assemble and necessarily requires mechanical joints between the filler neck and filler tube, as well as between the nozzle retainer and the filler neck. Any joint in a fuel filler tube assembly creates the possibility for vapor loss or fuel leaks through a defect or corrosion.
Moreover, with the necessity to assemble the parts post-manufacturing of the individual parts, variability in part dimensions—for example, the joints between the filler neck outlet and the filler tube and between the nozzle retainer and filler neck—as well as the quality of any sealing surfaces, can lead to an inferior product. Similarly, inconsistency in the orientation of features of the filler tube assembly, for example, thread orientation relative a fuel cap sealing surface or nozzle retainer orientation relative filler tube features, can lead to defective fuel filler tube assemblies through mistakes in the assembly process.